by Liz Szabo, USA TODAY

by Liz Szabo, USA TODAY

So once people start taking drugs to treat high cholesterol and hypertension - which can each reduce the risk of a second heart attack by 25% - many assume they no longer have to worry about eating their greens.

A new international study, however, shows that people with heart disease who adopt a healthy diet - in addition to taking their medications - cut their risk of dying from heart disease by an additional 35%.

In addition to reducing their risk of death, the healthy eaters in the nearly 4½-year study also cut their risk of another heart attack by 14%; a stroke by 19%; and congestive heart failure by 28%.

While doctors have studied diet's effect on the heart for years, before now, "we really didn't know if diet had additional beneficial effects, beyond that offered by the medication patients were taking," says study author and nutritionist Mahshid Dehghan.

"The benefit is real," says Dehghan, a researcher at McMaster University in Ontario, Canada. "We need to advise people that even a slight change in diet has a good effect. . . . It's never too late."

The nearly 32,000 patients in her study were taking medications such as aspirin, which helps prevent blood clots; cholesterol-lowering drugs such as statins; and blood pressure medications, such as angiotensin modulators and beta blockers.

Researchers asked patients from 40 countries how often they consumed certain foods during the past year, and followed them for 4½ years. Study authors defined healthy diets as ones with lots of fruits, vegetables, whole grains, nuts and fish, but less red meat and eggs.

About 80% of cardiovascular disease is preventable with diet and lifestyle, says registered dietitian Samantha Heller, at NYU Langone Medical Center in New York.

Researchers note their study has limitations. They observed what people were eating, and adjusted their findings for factors such as weight, smoking and exercise, which could potentially skew the results.

Still, they acknowledge that something other than diet could have lowered patient's heart disease risks. That's because the study wasn't a randomized controlled trial, the "gold standard" of medical evidence, in which patients are randomly assigned to follow one type of diet or another.

The landmark Lyon Heart Study, which randomly assigned heart attack survivors to follow the Mediterranean diet or their regular diet, found those eating Mediterranean diets reduced their risk of a second heart attack by 70%.

Yet definitive trials are difficult to perform, Dehghan says, because many people refuse to join, or cheat even if they do sign up.

Cardiologist Suzanne Steinbaum says many doctors fail to focus on diet once patients are on drugs.

The new study, she says, is a reminder that "diet is not a secondary part of the program. It is a mainstay in treatment," says Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York. "As much as we emphasize and stress the role of aspirin in prevention, we should give equal weight to a heart-healthy diet."